Battery protection system and method

ABSTRACT

A battery protection system for a battery having a switching mechanism positioned intermediate to the positive terminal and an electrical load of the battery. A controller manipulates the switching mechanism between an open position and a closed position, the closed position connects the electrical load to the battery and the open position disconnects the electrical load from the battery. The battery protection system utilizes a battery state-of-charge detection system, which instructs the controller to open the switching mechanism when the detection system detects a battery state-of-charge that is lower than a threshold value. The battery protection system is also equipped with a vehicle status detection system, which instructs the controller to close the switching mechanism when a vehicle startup condition is detected by the vehicle status detection system.

TECHNICAL FIELD

The present invention relates to an apparatus and method for determiningthe operational status of an automobile. In particular, the presentinvention provides a method and apparatus for protecting and maintainingthe charge within a battery.

BACKGROUND OF THE INVENTION

Motor vehicles, such as cars, marine vessels, trucks and the like almostuniversally include a battery that is used for engine ignition. Thebattery is also electrically connected to other electrical loads in thevehicle, such as hazard lights, radios, running lights, etc. Typically,a generator or alternator, driven by the engine, provides an electricalcurrent for recharging the battery.

Oftentimes, the engine is shutoff and the battery continues to drive anelectrical load in the vehicle and, in doing so, discharges the battery.In some cases, this can be inadvertent, such as leaving the headlightson, leaving the radio on, leaving the ignition keys in the accessory oron position, or through a malfunction in the electrical circuit. In anyevent and after a period of time, the battery will discharge to such anextent that engine cranking using the charge in the battery isimpossible.

Accordingly, and in order to maintain a minimal threshold charge valuein an automotive battery, it would be desirable to have a batteryprotection system which would disconnect the battery from an electricalload or draw, if the battery discharges below a set value. In addition,the system would need to distinguish the current status of theautomobile (i.e. engine running) and the type of electrical systemsbeing driven by the battery (i.e. hazard lights) in order to provide thesystem with a “fail-safe” protection system so that the battery is notdisconnected from driving critical systems.

Moreover, the system will also be required to determine when toreconnect the battery in order to drive such systems.

In connecting a battery to a supply of D.C. power of the same voltagerating such as a battery charger, the battery and supply must beconnected with their polarities matched. If the polarities aremismatched, a high-current condition might occur. The results will bepossible damage to the battery or damage to the electrical components ofthe vehicle.

A similar situation may occur when a motorist attempts to “jump start” avehicle having a dead battery, by using jumper cables to connect thedead battery to a vehicle having a fully charged battery. It isimportant that the positive terminal of the first battery be connectedto the positive terminal of the second battery, and likewise for thenegative terminals. However, it is not always possible to guaranteecorrect polarity matching. In a first situation, an unsophisticatedmotorist may not know how to properly connect the jumper cables. In asecond situation, it may be difficult to determine the polarities of thebatteries. This latter situation can occur when the polarity indicatingindicia on the batteries is covered with oil and dirt, at night when theindicia is difficult to read, or in the haste and frustration thatarises from attempting to jump start a car during extremely adverseweather conditions. Even under ideal circumstances, errors in matchingpolarities can still occasionally occur due to simple oversight.

In those instances in which polarities are mismatched during an attemptto start a stranded car, not only can the error cause damage to bothvehicle electrical systems, but such damage may result in both vehiclesbecoming disabled in a remote location. For these reasons, it is highlydesirable to prevent mismatching of battery polarities when a motoristis attempting to jump-start a stranded vehicle.

Accordingly, there is a need for a battery protection system thatprevents the damage to the battery from short circuits or improperjump-start conditions. In addition, there is also a need for a batteryprotection system wherein the battery maintains a minimal charge foroperating essential systems, such as the starter motor of an automobile.

SUMMARY OF THE INVENTION

A smart battery system designed to provide crank protection includesadditional features such as jump-start reverse polarity protection,short circuit protection and storage mode discharge protection.

The crank protection uses an electronic switch, i.e. FET, which opens todisconnect the battery from the vehicle electrical load to guaranteethat adequate cranking energy is always available. The reconnection ofthe battery is transparent to the user. A re-connect occurs when thebrake pedal is depressed, the hazard lights are turned on or the startermotor is turned on. If the hazard lights are activated, the batteryprotection system is inhibited from disconnecting the battery. If theengine is running, the battery protection system is inhibited fromdisconnecting the battery from the vehicle load. A manual switch isavailable to act as a backup.

If a dead short occurs between the battery negative and the positiveterminal of the battery protective system, as may happen in a crash, theelectronic switch opens, thus disconnecting the battery from the vehicleload. Additionally, if a jump-start is attempted with reverse polarity,the battery is disconnected. The short circuit and reverse polarityprotection features may be part of a simpler embodiment that does notinclude the crank protection features.

An exemplary embodiment of the inhibit-disconnect detection comprisesdetection of AC signals on the vehicle electrical load that representhazard light activation or engine running condition. The transparentdetection also detects transient changes in a DC voltage across thevehicle electrical load during FET open conditions.

An exemplary embodiment of a standalone short circuit and reversepolarity system includes the electronic switch and an excessive currentdraw detection condition. The excessive current draw detection would notinclude an engine start condition that normally has a relatively highcurrent condition.

The battery protection system includes a manual switch that allows thebattery protection system to be turned off. With this switch in the offposition, the battery is disconnected. With the switch in the onposition, the battery protection system is enabled.

The above-described and other features and advantages of the presentinvention will be appreciated and understood by those skilled in the artfrom the following detailed description, drawings, and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block diagram of an exemplary embodiment of theinvention;

FIGS. 2 and 3 illustrate the drain on a battery under engine startingconditions;

FIG. 4 illustrates a flow diagram of the exemplary embodiment of theinvention;

FIG. 5 illustrates an AC waveform of the battery voltage indicating anengine on condition;

FIG. 6 illustrates an AC waveform of the battery voltage indicating ahazard lights AC waveform;

FIG. 7 illustrates a block diagram of a transparent reconnect subsystem;

FIG. 8 illustrates an exemplary embodiment of a simplified jump-startprotection system; and

FIG. 9 is a flowchart illustrating portions of a command sequenceemployed by the control algorithm of the instant application.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The purpose of the battery protection system is to protect the batteryfrom discharge beyond the point where the remaining battery energy iscapable of starting the engine. This is accomplished according to analgorithm stored in a microprocessor that measures, among other things,the battery voltage, the ambient temperature, and time. Based upon thevalues of these inputs the microprocessor will disconnect the batteryfrom the load and/or electrical draw in order to preserve a minimalcharge value, namely, a sufficient amount of charge to provide crankingpower to the starter motor of the automobile. An automatic disconnect islatched by software, so that if the battery voltage recovers after thedisconnection, the battery remains disconnected.

The battery protection system is also configured to have a “fail-safe”operation in order to prevent the disconnection of the battery incertain situations; for example, if the engine is running or the hazardlamps are active. The system also utilizes a means for discriminatingthe AC waveforms that appear through the battery terminals, as a resultof engine ignition and hazard lamp activity. When these waveforms arepresent, the software using a pattern recognition algorithm to detectthese conditions, will then inhibit the disconnection of the batteryfrom occurring. For example, if the battery charging system should fail,allowing the battery to discharge below a point where the battery willbe unable to restart the automobile and the engine is running, thebattery would still be connected.

If the system has automatically disconnected the battery, it willautomatically reconnect the battery when the system senses someelectrical activity, such as the depression of the brake pedal (afunction that illuminates the taillights), turning on the ignition (afunction that manipulates the starter solenoid), and the activation ofthe vehicle hazard lamps. In other words, the system can detect whensomeone intends to start and drive the vehicle, and will accordingly,ensure that the battery is reconnected.

However and after a disconnect operation, the unit is prevented fromdetecting a reconnect condition for a time period of approximately 10seconds after the system disconnects the battery. This waiting period isprogrammed in the software in order to allow the voltage on the 12V busto “settle out” after the disconnection of the battery occurs.

When the battery is reconnected in response to a vehicle start uprequest, the system will allow up to 20 seconds for the engine to bestarted. Once 20 seconds has passed, and the battery charge is below thethreshold level for providing a charge to the starter motor, the batterymay again be disconnected automatically if the engine is not yet runningor the hazard lamps are not active.

A second function of the battery protection system is to automaticallydisconnect the battery in the event of excessively high battery current.Excessively high current would result from a short-circuit to chassis ofthe 12V bus as could occur in an accident, or from connecting anexternal battery incorrectly in an effort to jump-start the car. Adisconnection of this type is not inhibited even if the engine is on orthe hazard lights are on. When this sort of battery disconnection occurs(as opposed to the low-battery disconnect), the software disallows anautomatic reconnect. The only way to reconnect the battery in thissituation is to cycle an on/off switch of the battery protection system.

The battery protection system on/off switch can be used to manuallydisconnect the battery from the car (OFF), which virtually eliminatesany load presented to the battery (including the vehicle parasiticload). However, the unit will override this switch while the engine isrunning or the hazard lamps are active to prevent the driver fromdisconnecting the battery under these conditions. Also, the switch canbe used to cause a reconnect if needed (switch to OFF, then ON).

The battery protection system only requires electrical connections atthe battery terminals. No other electrical connections are required byvirtue of the fact that the reconnect signal, the hazards-on signal, andthe engine-on signal can all be detected through the battery terminals.

The battery protection system can be divided into seven sub-sectionsincluding: 1) battery disconnect-point determination; 2) over-currentdetection; 3) transparent reconnect detection; 4) engine-on/hazards-ondetection; 5) FET-array and ambient air temperature detection; 6) FETgate control; and 7) Manual switch/switch override. The microcontrollerreceives input for sections 1 through 5, and provides output to sections6 and 7.

The battery disconnect-point determination is accomplished in themicroprocessor by measuring the time-rate-of-change of the batteryvoltage and the ambient temperature, and comparing these measurements tobattery discharge curves stored in microprocessor memory. FIGS. 2 and 3illustrate typical time-rate of change curves. The battery voltage ismonitored by the microprocessor, via a voltage divider. If thestate-of-charge of the battery is such that any further reduction inbattery charge might disallow an engine start, the microprocessor willcause a field effect transistor (FET) array to turn off, therebydisconnecting the load from the battery.

The overcurrent detection is provided by a differential amplifier withinputs from the source and drain of the FET array. As such, thedifferential amplifier output is a voltage proportional to the currentthat flows through the FET array. A comparator output will go high ifthe FET current rises above the threshold, which is set at the negativeinput of an amplifier. Otherwise the amplifier output remains low.Whenever the amplifier output goes high, this will cause an immediateinterrupt in software within the microprocessor, to which themicroprocessor will respond by commanding the FET array to turn off. Themicroprocessor software will inhibit a reconnection from occurring afteran overcurrent disconnection has occurred. The only way to turn the FETarray back on in this case is to turn the battery protection system offand then back on with the manual on/off switch.

The transparent reconnect detection system operates after the FET arrayhas been commanded off due to low battery charge, by having a 6.2Kresistor that is in parallel with the FET array conduct up to 2 mA tothe vehicle loads. When the driver steps on the brake pedal (or turnsthe ignition switch to “start”, or turns on the hazard lamps), a stepchange in voltage occurs in the 6.2K resistor due to a fluctuation inthe load that is presented to the battery protection system. Thisstep-change in voltage is amplified by an amplifier U2C and then outputto a second amplifier. One amplifier input is filtered by the RC networkwhile the other input is not filtered. This causes a momentary voltagedifferential at the inputs of the amplifier, which causes the output ofamplifier to go high momentarily whenever the step-change occurs. A highoutput from the amplifier will cause an immediate interrupt to occur insoftware if the FET array was turned off due to a low battery.Otherwise, any output from amplifier is ignored by the microprocessor.This is set in the software. The microprocessor will respond to thisinterrupt by turning the FET array on. The software will maintain theFET array on for at least twenty seconds (unless an overcurrentcondition is detected) to allow the driver to start the car. Aftertwenty seconds, another battery disconnect could occur if the car hasnot been started or the hazard lamps are not active.

The engine-on/hazard-lights-on detection sub-system uses the ACcomponent of any signal that appears between the positive and negativebattery terminals as an input and amplifies it and then transmits it tomicroprocessor, which then samples this waveform in real time. When theengine is running, the waveform has a profile that is unique withrespect to frequency range and amplitude to any other components orconditions, which will create a signal between the positive and negativebattery terminals. Similarly, and if the vehicle's hazard lamps are on,the waveform profile generated is also unique. The microprocessorcompares the sampled waveform with data stored in memory in order todetermine whether the engine is running or the hazard lamps are on. Ifeither is the case, the software disallows a disconnection fromoccurring (except in the case of an overcurrent condition).

The FET gate control operates when the software determines that the FETarray should be turned on (battery connected). The microprocessorcommands that a circuit drive the gates of the FET array high. Thecircuitry contains a charge-pump, which provides an output that is about11V above battery voltage. This is required to allow the use ofN-channel FETs, which are significantly lower in cost than P-channel,but require that the gates be driven well above battery voltage in orderto fully turn them on. Conversely, when the software determines that theFET array should be turned off (battery disconnected), themicroprocessor commands the control circuitry to pull the FET gates toground.

The manual switch and/or switch override is mounted on the side of thephysical embodiment of battery protection system is used topower-up/down the battery protection system. All loads presented to thebattery are removed when the switch is in the off position, except forthe FET array leakage current. The switch off position would be selectedwhen the car is to be in long-term storage, because it virtuallyeliminates the vehicle parasitic load from the battery, which can be 20mA or more with the vehicle parked. Vehicle parasitic load can disablecranking ability in as little as two months.

However, it is important that the battery protection system ispowered-up while the engine is running or the hazard lamps are active,in order to keep the battery connected. Therefore, a transistor inparallel with the manual switch, and is commanded by software to bypassthe switch, thereby maintaining power while the engine is running or thehazard lamps are active.

Ambient and FET-array temperature detection is needed if the engineshould fail to start as expected during cranking, since it would bepossible to exceed the maximum allowable operating temperature of theFET array, leading to FET failure. To prevent this, a thermistor isattached to the FET array that provides a voltage proportional totemperature at the microprocessor. The microprocessor continuouslysamples this input, and if the temperature rises above the programmedlimit, the FET array will be turned off (unless, of course, the engineis running or the hazard lamps are active). After the FET array hascooled adequately, the software will command the FET array to turn onagain. Similarly, the ambient air temperature is monitored by themicroprocessor, and used in the determination of the battery-disconnectpoint (see above).

The condition of the battery under load is a function of several factorsincluding load, time under load, temperature of the battery, the age ofthe battery, the number of times the battery has been discharged and thelevel of discharge.

FIG. 1 is an exemplary embodiment of a complete battery protectionsystem 10. There are several features of a battery protection system.These include: crank protection, short circuit protection, reversepolarity protection and storage mode protection.

A basic element of the battery protection system is the use of one ormore electronic switches (FETs) in parallel that open and disconnect thevehicle electrical load under certain commands from the batteryprotection system. The advantage of an electronic switch overelectrically controlled mechanical switches is freedom of arcing underhigh current conditions. Mechanical switches are also subject tocontamination from environmental conditions that exist within a vehicleengine area.

Another key feature of the battery protection system is the reconnect ofthe battery that occurs without being evident to the user. The reconnectoccurs under at least three programmed conditions. These include:depressing the brake pedal, ignition switch “START”, and the activationof the hazard lights. A manual reconnect switch is available as a backup.

In addition, if the hazard lamps are activated or the engine is running,the battery protection system is inhibited from disconnecting thebattery from the vehicle load.

FIG. 1 illustrates an exemplary embodiment of battery protection system10. The positive terminal of a battery 12 is connected to a B+ input ofa circuit board (not shown) of battery protection system 10. Inaddition, the positive terminal of battery 12 is also connected to thedrain connections of a FET array 14. FET array 14 consists of aplurality of electronic switches (FETs) or gates. There are four suchFETs in the exemplary embodiment since a single FET is not capable ofhandling the current load. However, and depending upon the current loador anticipated current load, fewer or more FETs may be used in array 14.Moreover, and if a single FET is capable of carrying the anticipatedcurrent load, a single FET can be used.

The sources of the FETs are connected to a vehicle load 16. In addition,the gates of array 14 are coupled to the output of a gate drive circuitor FET driver 18. Vehicle load 16 is also connected to a load senseinput 20 of the battery protection system. The battery protection systemof the instant application only requires three connections to theautomobile wiring. This permits the battery protection system to bemounted onto the terminals of a battery with the positive connector ofthe load being connected to the output of the battery protection system.The output is electrically at the junction of the source terminals ofthe FETs and the junction noted as 20 in FIG. 1.

Fundamentally, the system provides a switch between the positiveterminal of the battery and the load. The FET gate signals are such thatfor a given battery and load condition, the FETs are opened thusdisconnecting the battery. It is important to note that resistor 22 isin parallel with the FET source and drain connections such that when theFETs create an open condition, a small amount of current less than 2milli-amperes flows from the battery through the load. An exemplaryvalue of the resistor is 6 Kohms. When the FETs are open, a change onthe load will appear as a voltage change on the load sense input 20. Anamplifier U2 24 provides the voltage change to an interrupt input of amicroprocessor 26.

An exemplary microprocessor is the 16C73 microprocessor made byMicrochip Corporation. This voltage sensing can be used to detect anoperator depressing a brake pedal or turning on the ignition switch.These actions instruct the microprocessor's output DOUT to instruct theFETs of array 14 to turn on via gate drive 18. Additionally, themicroprocessor will instruct the FETs of array 14 turn on or stayclosed, providing battery voltage to the load for starting the vehicle.

The main function of the battery protection system is to prevent thebattery from being drained beyond its capability to start the vehicle.The battery condition is primarily a function of the batteries currentcharge and the battery drain under load over a period of time. Thebattery voltage is coupled to an analog-to-digital input of themicroprocessor 26 via Q1, acting as a switch.

The microprocessor has a counter input 28 that is coupled to anoscillator 30 that provides time data to the microprocessor. Inaddition, the microprocessor receives an input from a differentialamplifier 32 that provides a voltage difference between the FET drainvoltage and the source voltage. This voltage is representative of thecurrent drain by the load. It is not necessary for the detection to behighly accurate. For the purposes of the battery protection system, itis only necessary to know an order of magnitude such as less than 1ampere, less than 10 amperes, less than 100 amperes, less than 1000amperes or less than 2000 amperes.

A second analog-to-digital input 34 is coupled to a first thermistorcircuit 36 to measure the battery temperature. As discussed above, themeasured battery temperature is used by the microprocessor 26 todetermine an appropriate battery voltage at which to operate the FETs ofarray 14.

A third analog-to-digital input 38 is coupled to a second thermistorcircuit 40. This thermistor measures the temperature of the FETs inorder to protect the FETs from damage from operating beyond theiroperating range. The temperature of concern is significantly above anyambient temperature that the automobile may find in use. Thetemperatures involved are excessive temperature caused by excessivecurrent flow through the FETs. An exemplary value of FET temperature cutoff is 150° C.

An EEPROM 42 provides the programming information to the microprocessor26 via input 44. Included in this program are the characteristics of thebattery type used with the vehicle. Based upon this programming, thesystem determines the battery voltage at which to disconnect the vehicleload.

The battery protection system has an ON/OFF switch 46 and a switchoverride transistor 40 in conjunction with microprocessor 26. Whenswitch 46 is closed, the battery voltage is connected to a 5 voltregulator 48 that provides power to the circuitry of the system. Inaddition, it provides the battery voltage to a voltage divider 50 thatis coupled to a VBAT input of the microprocessor, which converts the DCvoltage to a digital signal representative of the battery voltage. Anoutput 52 of microprocessor 26 provides a switch override function.

Using the battery voltage, the time of drain, the order of magnitude forthe current drain and the battery temperature, the microprocessordetermines a battery voltage level at which the gate drive 18 causes theFETs of array 14 to open and disconnect the vehicle load.

During normal operation of the vehicle, the vehicle's generator providesthe power for operating the vehicle. This in turn keeps the voltage atVBAT at a level above the cutoff voltage determined by the system. Whenthe engine is off and with no hazard light operation, the battery issubject to drainage depending upon the vehicle load caused by theoperator's inadvertent actions, such as leaving the headlights, insidelights or other accessory equipment on. The system measures the drainageby measuring the drop in voltage over a period of time. The relativecurrent level is also known by the measurement of the voltage across theFET drain to FET source terminals. Ambient air temperature is alsoknown. This data is inputted to the microprocessor at terminals 54, 28,34 and 56. If the microprocessor determines that a specific batteryvoltage has been reached, gate drive 18 instructs the FET switches toopen and disconnect the vehicle load from the battery.

However, as indicated above if certain conditions exist, themicroprocessor 26 is inhibited from disconnecting the vehicle load 16from the battery 12. An amplifier 58 is connected to microprocessor 26and provides an overriding function if the engine is on, being startedor the hazard lights are on. Presence of these signals will inhibit theswitching off of the FET switches. Additionally, amplifier 24 willdetect the activation of either of these devices to switch the FETs backon if the FET switches are in the off position.

In addition, and if the operator depresses the foot brake when the FETsare in the off position, the depressing of the foot brake will close aswitch that causes a rear light of the vehicle to attempt to illuminate.The illumination of the rear light will cause a change in the tricklecurrent through resistor 22. The change is detected by amplifier 24 andthe system will be instructed to wake up and reconnect the FET switcheslong enough for the operator to attempt to start the vehicle.

Accordingly, the amplifier and the microprocessor will detect the changein current through resistor 22, which is caused by that depression onthe foot brake.

The system's method of sensing the presence of ignition, hazard light onand other known conditions allows a high degree of confidence indistinguishing engine on and hazard light condition from otherelectrical activity. The engine on condition creates a specific noisecondition on the battery voltage that is detectable and different fromother noise and transient conditions in a vehicle's electrical system.

FIG. 5 illustrates the AC waveform created by the electrical system whenthe engine is on. FIG. 6 illustrates the AC waveform generated by thehazard lights when they are on. It is unlikely that any other part ofthe electrical system will generate an AC waveform with the AC amplitudeexhibited by the engine on or hazard lamps condition. The circuitry ofthe amplifier that detects the load fluctuation, which initiates abattery reconnect is comprised of two parts.

The first part is an amplifier that amplifies the AC waveform existingacross the vehicle electrical load at the junction 20 of the FETs sourceand the vehicle load. An exemplary value of 0.5 mv is a threshold atwhich the system detects an AC voltage change when the brake pedal isapplied. The gain of the amplifier is 500 creating a threshold voltageof 0.25 volts. The second part is a comparator that inputs the amplifiedthreshold voltage into a comparator. The comparator is set to create asquare wave pulse into an interrupt pin of the microcontroller.

Amplifier 58 receives the AC component of the signal present at junction20 due to the engine ignition or the hazard lamps activity. An exemplaryminimum value would be 50 mV peak-to-peak. Amplifier 58 transmits thissignal with a gain of 40 to a fourth analog-to-digital microprocessorinput. The frequency and amplitude of this signal is a function ofengine rpm or the on/off frequency of the hazard lights, and isdiscriminated by the microcontroller for use in inhibiting a batterydisconnect.

Prior art systems depended on connection to one or more externalcircuits for creating a switch for reconnect of the system once thebattery has been disconnected.

FIG. 7 illustrates a subsystem 60 of the battery protection system. Thetransparent reconnect subsystem is based upon detection of a transientchange to the DC level on the vehicle load. When the FET switches are inthe off position, as discussed above, a trickle current flows from thebattery through a resistor, with an exemplary value of 6000 ohms. As canbe seen on FIG. 1, this resistor is electrically across the drain tosource terminals of the FETs of array 14. When an operator opens thedoor, presses the brake pedal or turns on the ignition key, theseactions create a transient change to the DC voltage level across thevehicle load. This is true even though the voltage across the vehicleload is considerably lower than the battery voltage, due to the presenceof the 6000-ohm resistor in series between the battery and the vehicleload. Transparent reconnect subsystem comprises an amplifier 62 and acomparator 64. The time constant of capacitor 66 and resistor 68 allowsthe comparator to discriminate the transient changes in the DC level atthe junction of the vehicle load from normal electrical noise. Thistransient is amplified by operational amplifier U2C 24 and coupled tocomparator 64. The values of amplification and comparator set levels arepredetermined so that the comparator produces a reset pulse that iscoupled to an interrupt/reset input 70 of the microprocessor 26. Asdiscussed above, depressing the brake pedal, for example, will create atransient on the vehicle load during those times the FET switches areopen that is detected by the reconnect subsystem. If the batteryprotection system is operating in a mode whereby the FET switches areon, the microprocessor is programmed to ignore the pulses generated bythe transparent reconnect subsystem.

Another embodiment of the system may include a memory system 72 thatremembers the number of times and depth of discharge of the battery aswell as the age of the battery and in turn provides a calculation of thebattery life. This may be used to alert the operator that the batterymay be nearing the end of its useful life. No additional input data isrequired. The EEPROM 42 may provide the data about the battery installedin the car. No additional circuitry is required due to themicroprocessor's ability to write data to, and read the data from theEEPROM memory. It is advantageous to have a reset switch with the memoryto be used when the battery is replaced.

Another feature of the system is a subsystem that detects a dead shortbetween the positive terminal output across the vehicle load 16 and thenegative terminal of the battery 12. Such a short would create anexcessive current through the electronic switches of array 14. Theexcessive current is detected by a high current detection circuit 31,which instructs microprocessor 26 to open the electronic switches. Thisaction removes the excessive load on the battery 12.

The present invention is particularly well suited for use in anelectronics package that is powered by battery 12. For example, in apreferred and exemplary embodiment, the electronics package is part of asmart battery, wherein the electronics package is electrically connectedto a terminal(s) of battery 12. The electronics package of the smartbattery provides the user with a variety of functions and is capable ofstoring and monitoring information relating to battery performance andthe like. The electronics package requires power to operate and thus isconnected to the battery terminal. The terminal connector of the presentinvention preferably provides an electrical connection between aninternal electrical distribution assembly (not shown) within theelectronics package and a terminal of battery 12.

With the availability of large-scale integration it is likely that mostof the circuitry involved with the battery protection system may beincluded within a single integrated circuit. The system may include onecircuit board housing the control circuitry and a separate circuit boardholding the FET switches. The entire unit may be packaged so that it canbe mounted on the battery itself.

The embodiment of the invention shown in FIG. 1 also disconnects thebattery from the load when a jump-start is performed incorrectly. Ajump-start is defined as the starting of an internal combustion enginethat has a weak or discharged battery by means of booster cables. Anexemplary embodiment physical layout of the invention is such that thepositive terminal of the battery is not accessible so long as thebattery protection system is connected. However, the cable that normallyis connected to the positive terminal of the battery is connected to anoutput terminal of the battery protection system and the negativeterminal of the battery is connected to the chassis.

A vehicle having the battery protection system would hopefully neverneed a jump-start because of a discharged battery. However the circuitryof the system is such that an inadvertent reverse connection will causethe FET switches to open eliminating the cross connection. If anexternal source such as a charger, battery or the electrical system ofanother vehicle is connected such that the negative lead for theexternal source is connected at point A with the positive terminal ofthe external source connected to the chassis, the FETs will open, thuseliminating the short across the battery. Upon connection, the excessivecurrent condition will be detected by differential amplifier 32, whichcauses the comparator output to go high, which causes an interrupt inthe microcontroller. The microcontroller then causes the FET switch toopen. This will prevent the arcing and other deleterious effects areverse connection can cause.

Similarly, if due to a crash or other unusual event, a short circuitoccurs with the vehicle load 16, as shown in FIG. 1, the currentlimiting functions described above will disconnect the load from thebattery by opening the FET switches.

A simplified embodiment of the circuitry illustrated in FIG. 1 is shownin FIG. 8 as 110. This limited circuitry illustrates an embodiment thatis limited to prevention of the deleterious effects from improperjump-starting and short circuits within the vehicle load 116. In thisembodiment, the circuitry is limited to the FET switches of array 114, aregulated power supply 118, a High Current detector DifferentialAmplifier 122, a Latching Integrated Circuit 121, and a FET Gate DriveCircuit 120.

As discussed above, connecting an external source such as a charger,battery or another vehicle across points A and B, if inadvertently doneincorrectly will cause. excessive current to flow through the FETswitches. The excessive current will be measured as a voltage bydifferential amplifier 122, which, at a predetermined set point willcause the Latching Integrated Circuit to apply “ground” to the gates ofthe FET switches of array 114 via Gate Drive circuit 120. This willcause the FET switches of array 114 to open, disconnecting the batteryfrom the load, thus eliminating the short caused by the reverseconnection or the short within the vehicle load. A manual reset switchwould enable the user to reconnect battery. The current caused by such ashort or reverse connection is in excess of the current required forstarting the vehicle; therefore the predetermined value to cause thesystem to remove the battery is in excess of the starting currentrequired. An additional optional feature of the short or jump-startfacility of the simplified system or the full system is to include a LEDor other display device to indicate a short or reverse batterycondition.

FIG. 9 is a flowchart illustrating portions of a command sequenceemployed by the control algorithm of the instant application.

While the invention has been described with reference to a preferredembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof Therefore, it is intended that the invention notbe limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

What is claimed is:
 1. A battery protection system for a battery,comprising: an electronic switching device comprising a plurality ofelectronic switches positioned intermediate to a positive terminal of abattery and an electrical load; a controller for manipulating saidelectronic switching device between an open circuit position and aclosed circuit position, said closed circuit position connecting saidelectrical load to said battery and said open circuit positiondisconnecting said electrical load from said battery; a detectionsystem, said detection system instructs said controller to manipulatesaid electronic switching device into said open circuit position whensaid detection system detects a battery charge that is lower than athreshold value, said threshold value is a charge sufficient enough toprovide cranking power to an automobile engine; a short-circuitdetection system being capable of detecting a short-circuit situationwithin said electrical load of said battery, said short-circuitdetection system instructs said controller to manipulate said electronicswitching device into said open circuit position when said short-circuitdetection system detects said short-circuit; a manual override switchfor completely disconnecting said battery from any electrical load; abypass circuit being adapted to allow a bypass current to flow from thebattery when said electronic switching device is in said open circuitposition, said bypass current being incapable of supplying a startingvoltage to an engine of a vehicle into which the battery is installed; avehicle status detection system, said vehicle status detection systeminstructs said controller to manipulate said electronic switching deviceinto said closed circuit position when a battery re-connect condition isdetected in said bypass current by said vehicle status detection system;and a controller bypass system, said controller bypass system preventssaid controller from manipulating said electronic switching device intosaid open circuit position when a critical vehicle system is inoperation.
 2. A battery protection system as in claim 1, wherein saidshort-circuit detection system inhibits said controller from instructingsaid electronic switching device to said closed circuit position aftersaid short-circuit detection system detects said short-circuit.
 3. Abattery protection system as in claim 2, wherein said battery chargedetection system is also capable of detecting a reverse polaritysituation encountered by a terminal of said battery, said battery chargeprotection system instructs said controller to manipulate saidelectronic switching device into said open circuit position when saidbattery charge detection system detects said reverse polarity situation.4. A battery protection system as in claim 1, wherein said batteryre-connect condition is a depression of a brake pedal which illuminatesa taillight, the illumination of said taillight causing a currentfluctuation which is detected by said vehicle status detection system orthe movement of an ignition switch from an off position to a startposition, said start position causes a starter motor to activate, theactivation of said starter motor causes a current fluctuation which isdetected by said vehicle status detection system or the opening of a cardoor which illuminates an interior light, the illumination of saidinterior light causes a current fluctuation which is detected by saidvehicle status detection system.
 5. A battery protection system as inclaim 1, wherein said critical vehicle system is the activation of ahazard light of the vehicle or the engine, which is operating.
 6. Thebattery protection system as in claim 1, wherein the battery protectionsystem is an integral part of the battery.
 7. The battery protectionsystem as in claim 1, wherein the manipulation of the said electronicswitching device into said closed circuit position is transparent to thevehicle operator.
 8. A method for maintaining a minimal charge value ina battery of a vehicle, comprising: receiving a signal indicative of thecharge of the battery; receiving a signal indicative of the load on thebattery; receiving a signal indicative of the amount of time the loadhas been on the battery; predicting when the charge of the battery underthe present load will reach the minimal charge; disconnecting the loadfrom the battery before the charge of the battery will reach the minimalvalue by manipulating a plurality of electronic switches into an opencircuit position, while allowing a small by-pass current to remainconnected to the battery, the small by-pass current being insufficientto provide a starting voltage to the vehicle; disconnecting the loadwhen a short circuit condition has been detected; monitoring the smallby-pass current for a current fluctuation indicative of an actionrequiring battery reconnect; and reconnecting the battery to the load ina transparent manner when said current fluctuation is found.
 9. Themethod as in claim 8, wherein the current fluctuation is caused by anillumination of taillight, or the movement of an ignition switch from anoff position to a start position or the illumination of an interiorlight of the vehicle.
 10. The method as in claim 8, wherein the load isprevented from being disconnected when an engine of the vehicle isoperating or the hazard lights of the vehicle are operating.
 11. Themethod as in claim 9, wherein the load is prevented from beingdisconnected when an engine of the vehicle is operating or the hazardlights of the vehicle are operating.
 12. The method as in claim 8,further comprising disconnecting the load when a reverse polarity hasbeen detected at the terminals of the battery.
 13. The method as inclaim 11, further comprising disconnecting the load when a reversepolarity has been detected at the terminals of the battery.